Avian Influenza (H5N1) Outbreaks Seen in Dairy Herds Across the Country

This year the pathogen has found a new host, dairy cattle. There are several strains of avian influenza, the strain being observed in dairy herds is H5N1. It was first identified in dairy cattle in March 2024 in Texas. It has been confirmed in dairy herds across 12 states, with the number most likely much higher. Dairy producers are hesitant to test for it since it will affect their milk sales if found to be contaminated.

While the disease can be fatal in poultry, the clinical signs that have been observed in dairy cattle are far less severe. Common clinical signs are reduced appetite, reduced milk production, reduced rumination, nasal discharge, and thickened and discolored milk. While pasteurization does make the milk safe to consume, the reduced milk production and chance for change in consistency will reduce milk sales for the dairy farmer if their herd is contaminated.

The disease has become particularly concerning as it has been found to be transmissible from cows to humans. So far there are 3 total human cases from exposure to dairy cattle, 2 in Michigan and 1 in Texas. However, the number is likely higher due to many farm laborers not wanting to get tested, due to loss of wages and fear of immigration issues for undocumented workers. Human symptoms have been mild as well, but the virus could evolve to be more harmful. The first 2 cases saw only conjunctiva, infection and inflammation of the eyelid. The third case however saw respiratory symptoms such as coughing. This is cause for concern as respiratory symptoms allow for much easier transmission if the virus does evolve for human to human transmission. At the moment, it is hypothesized that the disease can only be transmitted to humans from cows, meaning one person cannot give another person the disease. Right now, the best way to prevent contamination in your herd is proper biosecurity.

Biosecurity Recommendations

• Clean and disinfect equipment - In addition to proper sanitation of equipment, provide adequate hygiene materials for workers such as gloves and handwashing stations
• Quarantine new cattle - Quarantine new or returning cattle for at least 21 days. Anyone who works with them should use separate clothing, equipment, boots etc. Quarantine animals should be worked with last. Ensure proper measures are biosecurity taken after working with the quarantined animals such as cleaning boots, hands, showering ASAP, etc.
• Isolate sick animals - Separate sick animals with as much distance as possible and follow the same biosecurity measures as with the quarantine animals when working with them. If you have both quarantine and sick animals, deal with the sick animals after the quarantine animals.
• Limit movements of cattle - Try to limit cattle leaving and coming into the farm as much as possible unless absolutely necessary
• Follow good milking practices - Proper sanitation of both the teats and milking equipment is essential. Milkers should follow proper biosecurity measures
• Limit vehicles and equipment - Try to have designated equipment for certain tasks and limit movement of vehicles and equipment coming on and off the farm
• Delay or stop non-essential visitors
• Avoid feeding raw milk to calves and other farm animals
• Feed only heat treated colostrum and pasteurized milk to calves and other animals

Avian influenza in dairy cattle is still a very new topic. Although not much is understood and clinical signs do not seem drastic, the dairy industry is taking the issue very seriously. In recent events we have seen how disease outbreaks can devastate public health and the economy. If everyone does their part to ensure proper biosecurity and educate themselves, hopefully we can move past this outbreak.

References

1. American Veterinary Medical Association. (N.D.). Avian Influenza. American Veterinary Medical Association. https://www.avma.org/resources-tools/animal-health-and-welfare/animal-health/avian-influenza
2. American Veterinary Medical Association. (2024). Avian Influenza. American Veterinary Medical Association. https://www.avma.org/resources-tools/animal-health-and-welfare/animal-health/avian-influenza/avian-influenza-virus-type-h5n1-us-dairy-cattle
3. National Milk Producers Federation. (2024). H5N1 in Dairy Cattle. National Milk Producers Federation. https://www.nmpf.org/resources/hpai#:~:text=While%20dairy%20cows%20that%20have,offset%20some%20of%20these%20losses.
4. Center for Disease Control. (2024). How CDC is monitoring influenza data among people to better understand the current avian influenza A (H5N1) situation. Center for Disease Control. https://www.cdc.gov/bird-flu/h5-monitoring/index.html

This article appears on July 2024, in Volume 5, Issue 1, of the Maryland Milk Moos newsletter.

Maryland Milk Moo's, July 2024, Vol. 5, Issue 1

Maryland Milk Moos is a quarterly newsletter published by the University of Maryland Extension that focuses on dairy topics related to Nutrition and Production, Herd Management, and Forage Production.

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